Methods for stabilizing bone using spinal fixation devices

ABSTRACT

A method of stabilizing bone, such as a spine, includes providing a coupling element having first and second sections that are angled relative to one another, the coupling element having rod receiving openings for securing an elongated member such as an orthopedic rod, and assembling the coupling element with an anchoring element. The method includes securing the anchoring element in bone, moving the coupling element relative to the anchoring element to align the rod receiving openings with the orthopedic rod, securing the orthopedic rod in the rod receiving openings, and after the securing step, locking the coupling element from further movement relative to the anchoring element.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a divisional of U.S. patentapplication Ser. No. 10/091,068 filed Mar. 5, 2002, which claims benefitof U.S. Provisional Application No. 60/322,042, filed Sep. 14, 2001, thedisclosures of which are hereby incorporated by reference herein.

FIELD OF THE INVENTION

[0002] The present invention relates generally to spinal fixationdevices and more specifically relates to pedicle fixation assemblies.

BACKGROUND OF THE INVENTION

[0003] The spinal column is a highly complex system of bones andconnective tissues that provides support for the body and protects thedelicate spinal cord and nerves. The spinal column includes a series ofvertebral bodies stacked one atop the other, each vertebral bodyincluding an inner or central portion of relatively weak cancellous boneand an outer portion of relatively strong cortical bone. Situatedbetween each vertebral body is an intervertebral disc that cushions anddampens compressive forces exerted upon the spinal column. A vertebralcanal containing the spinal cord and nerves is located behind thevertebral bodies.

[0004] There are many types of spinal column disorders includingscoliosis (abnormal lateral curvature of the spine), kyphosis (abnormalforward curvature of the spine, usually in the thoracic spine), excesslordosis (abnormal backward curvature of the spine, usually in thelumbar spine), spondylolisthesis (forward displacement of one vertebraover another, usually in a lumbar or cervical spine) and other disorderscaused by abnormalities, disease or trauma, such as ruptured or slippeddiscs, degenerative disc disease, fractured vertebra, and the like.Patients that suffer from such conditions usually experience extreme anddebilitating pain, as well as diminished nerve function.

[0005] Surgical techniques commonly referred to as spinal fixation usessurgical implants for fusing together and/or mechanically immobilizingtwo or more vertebral bodies of the spinal column. Spinal fixation mayalso be used to alter the alignment of adjacent vertebral bodiesrelative to one another so as to change the overall alignment of thespinal column. Such techniques have been used effectively to treat theabove-described conditions and, in most cases, to relieve pain.

[0006] There are many disadvantages associated with current spinalfixation devices. FIG. 1 show a prior art bone fixation device that isincapable of capturing spine rods when the rod capturing assemblies mustbe rotated to extreme angles. The design limits pivotal movement to anangle θ.

[0007] One spinal fixation technique involves immobilizing the spineusing orthopedic stabilizing rods, commonly referred to as spine rods,which run generally parallel to the spine. This may be accomplished byexposing the spine posteriorly and fastening bone screws to the pediclesof vertebral bodies. The pedicle screws are generally placed two pervertebra and serve as anchor points for the spine rods. Clampingelements adapted for receiving a spine rod therethrough are then used tojoin the spine rods to the pedicle screws. The aligning influence of thespine rods forces the spinal column to conform to a more desirableshape. In certain instances, the spine rods may be bent to achieve thedesired curvature of the spinal column.

[0008] U.S. Pat. No. 5,129,388 to Vignaud et al. discloses a spinalfixation device including a pedicle screw having a U-shaped head rigidlyconnected to an upper end of the screw. The U-shaped head includes twoarms forming a U-shaped channel for receiving a spine rod therein. TheU-shaped head is internally threaded so that a setscrew having externalthreads may be screwed therein. After the pedicle screw has beeninserted into bone and a spine rod positioned in the U-shaped channel,the set screw is threaded into the internal threads of the U-shapedchannel for securing the spine rod in the channel and blocking relativemovement between the spine rod and the pedicle screw. The fixationdevice also includes a cap covering an upper portion of the U-shapedhead to prevent the arms from spreading apart as the set screw isthreaded into the internal threads of the U-shaped head.

[0009] Surgeons have encountered considerable difficulty when attemptingto insert spinal fixation devices such as those disclosed in theabove-mentioned '388 patent. This is because the U-shaped heads atopadjacent screws are often out of alignment with one another due tocurvature of the spinal column and the different orientation of adjacentpedicles receiving the screws. As a result, spine rods must often bebent in multiple planes in order to pass the rods through adjacentU-shaped channels. This “bending the spine rod” solution serves toweaken the strength of the assembly and results in significantly longeroperations, which increases the likelihood of surgical complications.

[0010] In response to the above-noted problems, U.S. Pat. No. 5,733,286to Errico et al., U.S. Pat. No. 5,672,176 to Biedermann et al., and U.S.Pat. No. 5,476,464 to Metz-Stavenhagen disclose polyaxial spinalfixation devices wherein the anchoring element fixed to the bone has aspherically-shaped head. The fixation devices in the above-identifiedpatents also have orthopedic rod capturing assemblies for securingorthopedic rods in the capturing assemblies and connecting the rods withthe anchoring elements. The spherically shaped heads of the anchoringelements permit movement of the rod capturing assemblies relative to theanchoring elements.

[0011] In spite of the above-mentioned devices, there remains a need forimproved spinal fixation devices. In particular, there remains a needfor spinal fixation devices that provide an increased degree ofangulation between the rod capturing assemblies and the anchoringelements so as to facilitate capturing orthopedic stabilizing rodswithin the rod capturing assemblies.

SUMMARY OF THE INVENTION

[0012] In one preferred embodiment of the present invention, a fixationassembly includes a coupling element having a first section with a firstbore coaxial with a first longitudinal axis and a second section with asecond bore coaxial with a second longitudinal axis transverse to thefirst longitudinal axis. The first bore extends from an upper end of thecoupling element and the second bore extends from the lower end of thecoupling element. The coupling element also includes rod-receivingopenings extending from the upper end thereof. The fixation assemblyanchoring element having a first end for insertion into bone and alongitudinal axis. The first and second bores of the coupling elementextend in directions that are tilted with respect to one another, astheir associated first and second longitudinal axes are disposedtransversely to one another. Due to the biased angulation of thecoupling element, the coupling element can be manipulated to cover abroader range of angles for capturing an orthopedic stabilizing rod.

[0013] In certain preferred embodiments, the anchoring element isintegrally connected to a lower end of the coupling element. In otherpreferred embodiments, the anchoring element comprises a separate memberassembled with the coupling element, whereby the coupling element andanchoring element are pivotable and rotatable relative to one anotherfor capturing a spine rod in the rod receiving openings of the couplingelement.

[0014] Achieving sufficient angulation between anchoring elements whileengaging the orthopedic rod is essential for assemblies mounted inspines having abnormal curvatures. Sufficient angulation is alsoimportant in the cervicothoracic junction of the spine.

[0015] After being assembled together, the coupling element and theanchoring element are preferably pivotable and rotatable relative to oneanother. The coupling element preferably includes a seat adjacent thelower end thereof that is shaped to facilitate pivotal movement of thecoupling element and anchoring element relative to one another.

[0016] In certain preferred embodiments, the seat is shaped to allow thecoupling element to pivot with respect to the anchoring element. Beforethe coupling element is locked into place with respect to the anchoringelement, the coupling element is pivotable and rotatable for capturing aspine rod in the rod receiving openings thereof. The combination of thepivotable coupling element and the tilted arrangement of the first andsecond portions of the coupling element enable the coupling element tomove over a broader range of angles for capturing a spine rod.

[0017] The anchoring element preferably has a second end remote from thefirst end, and a head at the second end having an underside for engagingthe seat. The assembly preferably includes a locking element engageablewith the coupling element for locking the rod in the coupling element,after the rod has been received in the rod-receiving openings. Thelocking element forces the head against the seat of the coupling elementto lock the position of the coupling element with respect to theanchoring element.

[0018] The head may have a depression adapted to receive a driver fordriving the anchoring element into bone. The depression in the head maybe one or more slots or a hexagonal opening. The anchoring element mayinclude a neck between the head and the first end thereof. The neckpreferably has a reduced diameter portion for facilitating pivotalmovement of the coupling element and the anchoring element relative toone another. The reduced diameter neck may have a concave surfacelocated adjacent an underside of the head.

[0019] The head and seat may have many shapes. In certain preferredembodiments, the head has an underside with a convex shape for engagingthe seat. The seat may be defined by an interior wall of the couplingelement having an inwardly tapering conical shape. In other preferredembodiments, the seat may be defined by an interior wall of the couplingelement having a convex or spherical shape.

[0020] The coupling element preferably has an exterior surface, an upperend and a lower end, and rod-receiving openings that are open on theupper end and extend toward the lower end. The coupling elementpreferably has cuts formed between the exterior surface and therod-receiving openings for minimizing the width of the coupling element.As a result, adjacent coupling elements may be more closely packedadjacent one another, because the cuts result in the coupling elementshaving less width.

[0021] In certain preferred embodiments, the anchoring element is ascrew fastener having screw threads extending between the first andsecond ends thereof. The anchoring element may include barbs on an outersurface thereof so that withdrawal of the anchoring element from bone ishindered by the barbs. The anchoring element may also include anelongated shaft having holes defined therein for receiving bone graftmaterial or allowing ingrowth of bone. The anchoring element may alsoinclude a hook for anchoring into bone.

[0022] The coupling element may include a chamfer adjacent the firstbore for facilitating assemblies of the anchoring element with thecoupling element. The coupling element may have opening surfacesdefining the rod receiving openings and the chamfer may extend from oneof the opening surfaces to an inner surface defining the first bore.

[0023] In another preferred embodiment of the present invention, a bonefixation assembly includes a coupling element having an upper enddefining a first plane and having rod receiving openings, a lower enddefining a second plane that intersects the first plane, and at leastone bore extending between the upper and lower ends. The at least onebore is adapted to receive an anchoring element. The assembly includesan anchoring element having a first end insertable into bone that isassembled with the coupling element.

[0024] The head of the anchoring element preferably has one or moredepressions formed therein adapted for receiving a driver for drivingthe anchoring element into bone. The anchoring element preferablyincludes a reduced diameter neck for facilitating pivotal movement ofthe coupling element with respect to the anchoring element.

[0025] In further preferred embodiments of the invention, a couplingelement has an upper end and a lower end and comprises a first sectionextending from the upper end toward the lower end of the couplingelement. The first section has a first bore coaxial with a firstlongitudinal axis. The coupling element has a second section extendingfrom the lower end toward the upper end of the coupling element. Thesecond section has a second bore coaxial with a second longitudinal axistransverse to the first longitudinal axis. As a result, the first andsecond bores extend in directions that are angled relative to oneanother. The coupling element includes rod-receiving openings extendingfrom the upper end toward the lower end that are adapted to receive anorthopedic rod.

[0026] The inner surface of the coupling element adjacent upper endpreferably includes threads for engaging external threads on a lockingelement for locking an orthopedic rod with the coupling element. Thelocking element is threaded into the internal threads of the couplingelement after spine rod has been captured in rod receiving openings.

[0027] In certain preferred embodiments, the coupling element has anouter surface with gripping notches for engagement by an instrument sothat the coupling element may be positioned with respect to anorthopedic rod. The notches may include indentations or protrusionsprovided therein for centering the instrument on the coupling element.

[0028] In still another preferred embodiment of the present invention, acoupling element for a pedicle screw assembly comprises an upper enddefining a first plane, a lower end defining a second plane, and atleast one bore extending between the upper and lower ends adapted toreceive an anchoring element. The first and second planes intersect oneanother. The first plane and the second plane preferably have anintersection defining an angle of about 20-30°. In more preferredembodiments, the angle between the first and second intersecting planesis about 25°±2°. In highly preferred embodiments, the angle between theintersecting planes is approximately 24°.

[0029] In yet another preferred embodiment of the present invention, acoupling element for a pedicle screw assembly includes a first sectionat an upper end of the coupling element, the first section having afirst bore coaxial with first longitudinal axis, and a second section ata lower end of the coupling element, the second section having a secondbore coaxial with a second longitudinal axis. The first and secondlongitudinal axes preferably intersect one another. The assemblyincludes an anchoring element, such as a screw thread. The boneanchoring portion of the anchoring element is adapted to project throughthe second bore opening at the lower end of the coupling element whenthe coupling element and anchoring element are assembled together.

[0030] In still another preferred embodiment of the present invention, amethod of stabilizing bone, such as an area of the spine, includesanchoring an anchoring element into bone. The anchoring element isassembled with a coupling element having first and second sections thatare angled relative to one another. In one preferred embodiment, theanchoring element has a first bore and a second bore that are tiltedwith respect to one another. The anchoring element projects through thesecond bore opening at a lower end of the coupling element so that thecoupling element and anchoring element are movable relative to oneanother. The position of the coupling element is adjustable with respectto the anchoring element so that rod receiving openings extending froman upper end of the coupling element may receive an orthopedic rod.After the rod is captured in the rod-receiving openings, the position ofthe coupling element is locked with respect to the anchoring elementusing a locking element that exerts a downward locking force on thespine rod, which in turn forces the head of the anchoring element intothe seat of the coupling element.

[0031] The coupling element desirably has the first bore extendingthrough the first section and the second bore extending through thesecond section. The anchoring element and coupling element arepreferably assembled by inserting the anchoring element into the firstbore.

[0032] Before the coupling element and anchoring element are locked, theposition of the coupling element may be adjusted by pivoting thecoupling element with respect to the anchoring element so that the rodreceiving openings engage an orthopedic rod disposed at a positiondisplaced from the longitudinal axis of the anchoring element.

[0033] In another preferred embodiment of the present invention, amethod of stabilizing bone includes providing a coupling element havingfirst and second sections that are angled relative to one another, thecoupling element having rod receiving openings for receiving anelongated member, assembling the coupling element with an anchoringelement, and after the assembling step, securing the anchoring elementin bone. The method includes moving the coupling element relative to theanchoring element to align the rod receiving openings with the elongatedmember, securing the orthopedic rod in the rod receiving openings, andafter the securing step, locking the coupling element from furthermovement relative to the anchoring element.

[0034] In still another preferred embodiment of the present invention, amethod of stabilizing an area of the spine includes providing a couplingelement having a first bore coaxial with a first longitudinal axis and asecond bore coaxial with a second longitudinal axis, whereby the firstand second longitudinal axes are transverse to one another. The methodincludes assembling the coupling element with an anchoring element, andafter the assembling step, securing the anchoring element in bone. Thecoupling element desirably has rod receiving openings for securing anorthopedic rod. The method also preferably includes moving the couplingelement relative to the anchoring element to align the rod receivingopenings with the orthopedic rod, securing the orthopedic rod in the rodreceiving openings, and after the securing step, locking the couplingelement from further movement relative to the anchoring element.

[0035] In yet another preferred embodiment of the present invention, amethod of stabilizing a spine includes providing a coupling elementhaving an uppermost end defining a first plane, a lowermost end defininga second plane, and at least one bore extending from the uppermost endtoward the lowermost end, whereby the first and second planes intersectone another. The method desirably includes assembling the couplingelement with an anchoring element, and after the assembling step,securing the anchoring element in bone. The method may also includemoving the coupling element relative to the anchoring element to alignrod receiving openings of the coupling element with an orthopedic rod,securing the orthopedic rod in the rod receiving openings, and after thesecuring step, locking the coupling element from further movementrelative to the anchoring element.

[0036] These and other preferred embodiments of the present inventionwill be described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] These and other objects, features and advantages of the presentinvention will be more readily apparent from the detailed description ofpreferred embodiments set forth below, taken in conjunction with theaccompanying drawings, in which:

[0038]FIG. 1 shows a side elevation view of a prior art bone fixationassembly.

[0039]FIG. 2 shows a simplified view of a pair of bone fixationassemblies coupled with an orthopedic stabilizing rod, in accordancewith certain preferred embodiments of the present invention.

[0040]FIG. 3 is a top plan view of a coupling element of a bone fixationassembly, in accordance with a preferred embodiment of the presentinvention.

[0041]FIG. 4 is a left side elevation view of the coupling element ofFIG. 3.

[0042]FIG. 5 is a front elevation view of the coupling element of FIGS.3-4.

[0043]FIG. 6 is a perspective view of the coupling element of FIGS. 3-5.

[0044]FIG. 7 is a cross-sectional view of the coupling element of FIG. 5taken along line 7-7 thereof.

[0045]FIG. 8 is a front elevation view of an anchoring element, inaccordance with certain preferred embodiments of the present invention.

[0046]FIG. 9 is a top plan view of the anchoring element of FIG. 8.

[0047]FIG. 10 is a right side elevation view, partially in section, ofthe anchoring element of FIGS. 8-9 partially assembled with the couplingelement of FIGS. 3-7.

[0048]FIG. 11 is a right side elevation view, partially in section, ofthe coupling element and anchoring element of FIG. 10 during a furtherassembly step.

[0049]FIG. 12 is a right side elevation view, partially in section, ofthe coupling element and anchoring element of FIG. 11, whereby theanchoring element is fully seated in the coupling element.

[0050]FIG. 13 is a right side elevation view, partially in section, ofthe coupling element and anchoring element of FIGS. 10-12, with theanchoring element secured in bone.

[0051]FIG. 14 is a right side elevation view, partially in section, ofthe coupling element and anchoring element of FIG. 13, with the couplingelement pivoted about a head of the anchoring element.

[0052]FIG. 15 is a right side elevation view, partially in section, ofthe bone fixation assembly of FIG. 14 with a spine rod captured in thecoupling element and held in place by a locking element.

[0053]FIG. 16 is a front elevation view, partially in section, of thecoupling element, anchoring element, of locking element and spinal rodshown in FIG. 16.

[0054]FIG. 17 is a cross-sectional view of an anchoring element of abone fixation assembly, in accordance with another preferred embodimentof the invention.

[0055]FIG. 18 is a perspective view of a coupling element of a bonefixation assembly, in accordance with another preferred embodiment ofthe present invention.

[0056]FIG. 19 is a right side elevation view of the coupling element ofFIG. 18.

[0057]FIG. 20 is a top plan view of the coupling element of FIGS. 18-19.

[0058]FIG. 21 is the cross-sectional view of the coupling element ofFIG. 20 taken along line 21-21 in FIG. 20.

[0059]FIG. 22 is the cross-sectional view of the coupling element ofFIG. 21 taken along line 22-22 in FIG. 21.

[0060]FIG. 23 is an elevation view of two bone fixation assembliessecured to a stabilizing rod, in accordance with preferred embodimentsof the present invention.

[0061]FIG. 24 is a perspective view of the two bone fixation assembliesof FIG. 23.

[0062]FIG. 25 is a perspective view of a coupling element of a bonefixation assembly, in accordance with further preferred embodiments ofthe present invention.

[0063]FIG. 26 is a cross sectional view of the coupling element of FIG.25.

[0064]FIG. 27 is a top view of the coupling element of FIG. 26 takenalong axis B-B thereof.

[0065]FIGS. 28A and 28B show respective top plan and side elevationviews of a blank used to make a coupling element of a bone fixationassembly, in accordance with certain preferred embodiments of thepresent invention.

[0066]FIG. 29 shows a front elevation view of a coupling element, inaccordance with certain preferred embodiments of the present invention.

[0067]FIG. 30 shows a top plan view of the coupling element of FIG. 29along axis A-A thereof.

[0068]FIG. 31 shows a side elevational view of the coupling element ofFIG. 29.

[0069]FIG. 32A shows a top plan view of the coupling element of FIG. 31along axis B-B thereof.

[0070]FIG. 32B shows a cross-sectional view of the coupling element ofFIG. 32A taken along line 32B-32B thereof.

[0071]FIG. 32B-1 shows an expanded view of a section of the couplingelement shown in FIG. 32B.

[0072]FIG. 33 shows a perspective view of an anchoring element of a bonefixation assembly, in accordance with certain preferred embodiments ofthe present invention.

[0073]FIG. 34 shows a top plan view of the anchoring element shown inFIG. 33.

[0074]FIGS. 35A and 35B show respective side elevation andcross-sectional views of the anchoring element shown in FIG. 33.

[0075]FIGS. 36A-36C show respective perspective, top plan andcross-sectional views of a locking element threadable into the couplingelement of FIGS. 29-32B-1, in accordance with certain preferredembodiments of the present invention.

[0076]FIG. 37A shows an exploded view of a bone fixation assemblyincluding a coupling element, a fastening element and a locking element,in accordance with certain preferred embodiments of the presentinvention.

[0077]FIGS. 37B and 38 show respective side elevation and frontelevation views of the bone fixation assembly of FIG. 37A after thecoupling element, anchoring element and locking element have beenassembled together.

[0078]FIG. 39 shows a cross-sectional view of the bone fixation assemblyshown in FIG. 37B.

[0079]FIG. 40 shows a fragmentary view of a driver including a lower endhaving spaced fingers for engaging a head of an anchoring element, inaccordance with certain preferred embodiments of the present invention.

[0080]FIG. 41 shows a cross-sectional view of the driver of FIG. 41engaging the head of the anchoring element.

[0081]FIG. 42 shows a perspective view of the driver of FIG. 42 engagingthe head of the anchoring element.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0082] Referring to FIG. 2, the present invention is generally relatedto providing bi-axial coupling elements that are capable of pivotingover a broader range of angles (e.g. to an angle θ₂ of up to about110°), thereby providing for greater angulation than is possible withthe prior art devices shown in FIG. 1.

[0083]FIGS. 3-16 show a bone fixation assembly, in accordance withcertain preferred embodiments of the present invention. The bonefixation assembly may be secured to the pedicles of vertebral bodies ofa spinal column. Referring to FIGS. 3-7, the fixation assembly includesa coupling element 12 preferably made of a biologically inert material,preferably any metal customarily used for surgical devices andparticularly those used for bone screws and pins, such as titanium orstainless steel. Other suitable materials for the coupling elementinclude alloys, composite materials, ceramics or carbon fiber materials.Coupling element 12 has an upper end 14 and a lower end 16. The upperend 14 defines a first plane 23 and the lower end 16 defines a secondplane 25, the first and second planes 23, 25 preferably intersecting oneanother.

[0084] The coupling element 12 includes a first section 18 that extendsfrom upper end 14 to an intermediate region 20, and a second section 21that extends from intermediate region 20 to lower end 16. The firstsection 18 has a first bore extending therethrough, which is coaxialwith a first longitudinal axis 22. The second section 21 has a secondbore extending therethrough, which is coaxial with a second longitudinalaxis 24. The first and second longitudinal axes 22, 24 are preferablyangled relative to one another. As a result, the first bore extendingthrough the first section 18 has an orientation that is non-parallel ortilted in relation to the second bore extending through the secondsection 21 (see FIG. 4).

[0085] Referring to FIG. 4, the angle ∝ formed between the first andsecond longitudinal axes 22, 24 may comprise any angle greater than 0°up to but not including 90°. The specific angle α may depend upon theparticular application for the fixation assembly 10. Preferably, theangle α is approximately between 20-30°. In more preferred embodiments,the angle α is approximately 25°±2°. In highly preferred embodiments,the angle α is approximately 24°. The coupling elements 12 may beprovided in a set, with each coupling element 12 having a slightlydifferent shape and unique angle. During surgery, a surgeon may select acoupling element from the set having an appropriate angle for theparticular patient and/or the particular location along a patient'sspine.

[0086] The coupling element 12 may have other shapes, such as aPolyaxial structure having more than two cylinders (e.g., three), witheach cylinder transverse to the other cylinders. In other preferredembodiments, the cylinders may have non-circular cross-sectional shapes,such as square, pentagonal, elliptical, etc.

[0087] Referring to FIGS. 5-7, coupling element 12 also desirably has asubstantially cylindrical outer surface 26 that extends from upper end14 to a convex surface 28 adjacent lower end 16. Coupling element 12also preferably includes one or more notches 30 formed in outer surface26 so that coupling element 12 may be secured by a tool, such as apersuader instrument. The notches 30 preferably extend in directionstransverse to the first longitudinal axis 22.

[0088] Referring to FIG. 7, coupling element 12 has an inner surface 38surrounding the first bore 40, which extends from upper end 14 towardlower end 16 and is preferably coaxial with first longitudinal axis 22.The inner surface 38 preferably includes internal threads 44 extendingfrom upper end 14 toward lower end 16. The coupling element 12 hassecond bore 41 that extends from lower end 16 toward upper end 14. Thesecond bore 41 is coaxial with second longitudinal axis 24.

[0089] Referring to FIGS. 5-6, coupling element 12 has a pair of rodreceiving openings 42 that extend from outer surface 26 to inner surface38, each rod receiving opening 42 communicating with first bore 40. Therod receiving openings 42 are adapted to capture and seat an orthopedicstabilizing rod therein. The rod receiving openings 42 preferablycomprise U-shaped openings having the respective open ends adjacentupper end 14 of coupling element 12 and the respective closed endsremote from the open ends.

[0090] The rod-receiving openings divide coupling element 12 into afirst arm 31A on one side of the openings 42 and a second arm 31B on anopposite side of the rod-receiving openings 42. The rod-receivingopenings 42 preferably include cuts 32 formed adjacent outer surface 26of coupling element 12. Although the present invention is not limited byany particular theory of operation, it is believed that the cuts 32enable two or more coupling elements 12 to be packed closer togetherthan would be possible for coupling elements having the cuts omitted.

[0091] Referring to FIGS. 6 and 7, the coupling element 12 preferablyhas a chamfer 45 that extends from upper end 14 toward an internalcavity 46. The chamfer 45 preferably extends between the opening surface43 of one of the rod receiving openings 42 to the inner surface 38 onthe first section 18. The chamfer 45 facilitates the insertion of ananchoring element into the coupling element 12; notwithstanding theangle of first bore 40 with respect to second bore 41. In certainpreferred embodiments, the chamfer 45 is bored out of the material ofcoupling element 12 to essentially form a third axis that is coaxialwith second bore 41 and second axis 24. The chamfer 43 preferablyprovides room for an anchoring element and driver to pass therethroughwhen securing the anchoring element in bone. In other preferredembodiments, the dimensions of the coupling element and anchoringelement may be selected to allow the anchoring element to be insertedinto the coupling element, without requiring a chamfer.

[0092] Referring to FIG. 7, coupling element 12 includes a seat 50adjacent lower end 16 for engaging an anchoring element. The seat 50preferably has a conical shape with sidewalls 52 tapering inwardlytoward lower end 16. In other preferred embodiments, the seat 50 issubstantially spherical or concave in shape.

[0093] Referring to FIGS. 8-9, the fixation assembly preferably includesan anchoring element 52, such as a screw fastener, having a tip end 54for insertion into bone, a head 56 at an upper end thereof, and externalscrew threads 58 that extend between tip end 54 and head 56. The screwthreads 58 have an inner diameter 64 and an outer diameter 66. The screwthreads 58 desirably terminate at a neck 60 preferably located betweenhead 56 and screw threads 58. The neck has a neck diameter 68 that isless than the outer diameter 66 of the screw threads. The reduceddiameter neck 60 allows the coupling element 12 to pivot and rotatethrough a broader range of motion relative to anchoring element 52. Theanchoring element 52, including the screw threads 58, neck 60 and head56, are preferably made of a biologically inert material, such astitanium or stainless steel.

[0094] Head 56 desirably includes one or more depressions or grooves 70adapted to cooperate with a driver used to screw the anchoring element52 into bone. Head 56 is preferably sized and shaped to pass through thefirst and second bores formed in coupling element 12 until an undersideof head engages the seat 50 (FIG. 7) of the coupling element. The head56 has an underside 57 that is preferably convex or spherical in shapefor engaging the seat 50. When the underside 57 of head 56 engages theseat, the tip end 54 and threaded portion 58 of the anchoring element 52extend through the second bore 41 (FIG. 7) at the lower end 16 ofcoupling element 12.

[0095] Referring to FIGS. 10-12, in one preferred method for assemblinganchoring element 52 with coupling element 12, the tip end 54 ofanchoring element 52 is passed through first bore 40 toward lower end 16so that screw threads 58 project from the lower end 16 of couplingelement. In certain preferred embodiments, the anchoring element 52 maypass freely through first bore 40 because the outer diameter of thescrew threads 58 may be less than the diameter of first bore 40. Inother preferred embodiments, the diameter of the threads 58 issubstantially similar to the diameter of first bore 40, requiring theanchoring element to be threaded into the coupling element until theunderside 57 of head 56 engages seat 50. In certain preferredembodiments, the underside 57 of head 56 is spherical and the seat isconical-shaped. In other embodiments, the underside 57 of head 56 andseat 50 comprise other shapes, such as a convex underside and a concaveseat.

[0096] Referring to FIGS. 13 and 14, after anchoring element 52 has beenassembled with coupling element 12, anchoring element 52 and couplingelement 12 are free to pivot and rotate relative to one another. Theneck 60 of anchoring element 52 preferably has a reduced diameter with aconcave outer surface 62 so that anchoring element 52 and couplingelement 12 may pivot over a broader range of angles relative to oneanother, as compared to an anchoring element on which a reduced diameterneck is omitted. FIG. 13 shows coupling element 12 in a first positionwith respect to anchoring element 52. FIG. 14 shows coupling element 12in a second position with respect to anchoring element 52 after couplingelement has been rotated counterclockwise relative to the position shownin FIG. 13.

[0097] After anchoring element 52 and coupling element 12 have beenassembled together, the subassembly is ready to be inserted into bone80. In one preferred embodiment, a pilot hole is drilled in bone, andanchoring element 52 is placed in the pilot hole and screwed into thebone 80 using a driver or tool. As anchoring element 52 is rotated bydriver, the anchoring element advances longitudinally into the bone 80.The anchoring element 52 is preferably advanced into the bone 80 untilit is firmly secured in place such as when the neck 60 of anchoringelement is adjacent the bone 80. In other preferred embodiments, the tipend includes a cutting edge formed therein such as a cutting flute, sothat pre-forming a pilot hole is not required.

[0098] After anchoring element 52 is anchored in bone 80, couplingelement 12 remains free to pivot and rotate relative to anchoringelement 52 so that an orthopedic stabilizing rod 82 may be capturedwithin the rod receiving openings 42 of coupling element 12. In certainpreferred embodiments, after the anchoring element has been fullyinserted into bone, a gap may exist between the lower end 16 of couplingelement 12 and bone 80. The gap preferably facilitates pivotal androtational movement of coupling element 12 relative to anchoring element52. In other preferred embodiments, the lower end 16 of coupling element12 may engage bone during a stabilizing procedure when the rod 82 iscaptured by coupling element 12. In these embodiments, however, it isnot critical that the lower end 16 of the coupling element 12 contactbone in order to form a reliable assembly. In other preferredembodiments, it may be necessary for the lower end 16 of couplingelement 12 to engage bone to provide a reliable, stable assembly. Thecoupling element 12 may be moved (e.g. pivoted) by grasping the couplingelement with a tool.

[0099] Referring to FIG. 15, after rod 82 has been positioned withincoupling element 12, a locking element 84 such as a set screw havingexternal threads, is threaded into internal threads 44 of couplingelement 12 until an underside 85 of locking element 84 abuts against rod82. Locking element 84 is then further tightened for forcing rod 82against the closed ends of the rod receiving openings 42. The tightenedlocking element 84 applies a downward force through rod 82 onto the topside 59 of head 56. In other embodiments, the coupling element 12 hasthreads on its outer surface 26 and the locking element comprises aninternally threaded sleeve.

[0100] Referring to FIGS. 15-16, the downward force applied by rod 82 tothe top side 59 of head 56 forces the underside 57 of head 56 into theseat 50 of coupling element 12. In embodiments in which the seat 50 hasa conical shape and the underside 57 has a spherical shape, engagementof the underside 57 with the seat 50 creates a spherical/conical surfacefriction lock that locks the position of the coupling element 12relative to the head 56, thereby preventing further pivotal and rotarymovement of the coupling element 12 and anchoring element 52 relative toone another. Although the present invention is not limited by anyparticular theory of operation, it is believed that the engagement ofthe spherical underside of the head with the conical seat of thecoupling element is a dramatic improvement over a convex/concaveinterface and dramatically improves the locking force exerted at theinterface of the screwhead and the coupling element. In otherembodiments, both seat 50 and underside 57 of head 56 have sphericalshapes.

[0101] In the prior art, it has been observed that some patients haverelatively small vertebrae, making it difficult to secure two or morebone fixation assemblies next to each other over adjacent vertebrae. Asa result, in some patients, one or more vertebrae may not have a sectionof a stabilizing assembly attached thereto. This situation may adverselyaffect stabilization and fusion of a spine segment because the entireportion of the spine segment is not being stabilized. Although thepresent invention is not limited by any particular theory of operation,it is believed that providing cuts 32 adjacent the rod receivingopenings 42 reduces the profile or width of the coupling element 12,thereby minimizing interference with neighboring coupling elements whena series of coupling elements are connected with a spine rod. The cuts32 allow the coupling elements to be packed tightly together, therebyimproving fusion of a spinal segment. Providing cuts 32 on couplingelement 12 also minimizes the occurrence of sharp edges that mayirritate a patient's tissue or cut through the surgical gloves ofmedical personnel.

[0102] In certain preferred embodiments, the head of the anchoringelement preferably has an underside defining a first radial surface anda top side defining a second radial surface, as disclosed in certainembodiments of U.S. patent application Ser. No. 09/755,846, thedisclosure of which is hereby incorporated by reference herein. Thesecond radial surface has a radius that is smaller than the radius ofthe first radial surface, which is believed to provide a lower overallsilhouette for the assembly.

[0103] Referring to FIGS. 18-22, in other preferred embodiments,coupling element 122 includes a first bore 140 extending through a firstsection 118 coaxial with a first longitudinal axis 122 and a second bore141 extending through a second section 121 a second longitudinal axis124, the first and second axis defining an angle coaxial with β that maycomprise any angle greater than 0° up to but not including 90°.Preferably, an angle of between 20-30° is used. In more preferredembodiments, the angle β is preferably about 25°±2°. In highly preferredembodiments, the angle β is preferably 24°.

[0104] The present invention also preferably includes a driver, such asthat disclosed in certain embodiments of U.S. patent application Ser.No. 09/755,846, filed Jan. 5, 2001, the disclosure of which is herebyincorporated by reference herein. The driver preferably has a rotatableshaft and one or more fingers extending from an end of the shaft forengaging the grooves in the head of the anchoring element. In preferredembodiments, the driver has one finger for each groove in the head ofthe anchoring element. The driver may also have external threads on ashaft that are adapted for engaging the internal threads of the couplingelement when the anchoring element is anchored to bone. The engagementof the external threads of the driver and the internal threads of thecoupling element generally stabilizes the assembly when the anchoringelement is secured to bone. Specifically, the engagement of the threadsprevents the coupling element from moving relative to the anchoringelement when driving the anchoring element into bone, therebyfacilitating bone anchoring.

[0105] The anchoring element may have expandable head, such as theexpandable head disclosed in certain preferred embodiments of commonlyassigned U.S. patent application Ser. No. 09/414,272, filed Oct. 7,1999, the disclosure of which is hereby incorporated by referenceherein. The expandable head has a recess and at least one slot extendingbetween inner and outer surfaces of the head, which facilitatesexpansion of the head. The anchoring element of the '272 patent also hasan insert which can be positioned at least partially in the recess, theinsert having an outer surface and defining an outer dimension that isgreater than the inner dimension of the recess. After a spinal rod hasbeen positioned within a coupling element, a locking element associatedwith the coupling element locks the orthopedic rod in the rod-receivingopening. The locking element forces the orthopedic rod into the rodreceiving opening, to in turn force the insert into the recess of theexpandable head. As the insert is forced into the recess, the outerdimension of the insert bears against the inner dimension of the head,thereby expanding the outer surface of the head against a seat of thecoupling element for locking the coupling element from further pivotalmovement.

[0106] As shown in FIG. 23, pedicle fixation assemblies 110A, 110B maybe mounted adjacent one another so as to engage a spinal rod 82. Asshown in FIG. 24, the anchoring elements 152A, 152B may be locked inplace with respect to the coupling elements 112A, 112B so as to formangles with respect to the spinal rod 82, in the xy, xz, or yz planes.

[0107]FIGS. 25-27 show a coupling element 212 for a pedicle fixationassembly in accordance with another preferred embodiment of the presentinvention. Coupling element 212 has an upper end 214 and a lower end216, the upper end 214 defining a first plane 223 and the lower end 216defining a second plane 225, the first and second planes 223, 225intersecting one another.

[0108] Referring to FIGS. 26-27, coupling element 212 has a first bore240 that extends along first axis 222 from upper end 214 to anintermediate region 220, and a second bore 241 that extends along secondaxis 224 from lower end 216 of coupling element 212 to intermediateregion 220. The first bore 240 and second bore 241 are generallyoriented non-parallel or transverse to one another.

[0109] The angle θ between first axis 222 coaxial with first bore 240and second axis 224 coaxial with second bore 241 may comprise any anglegreater than 0° up to but less than 90°. The angle θ may vary dependingupon the particular application for the coupling element 212.Preferably, the angle θ is approximately between 20-30°. In morepreferred embodiments, the angle θ is approximately 25°±2°. In highlypreferred embodiments, the angle θ is approximately 24°.

[0110] Referring to FIG. 25, coupling element 212 desirably has an outersurface 226 that is cylindrical in shape, extending from upper end 214to lower end 216. Outer surface 226 preferably includes one or morenotches 230 formed therein so that coupling element 212 may be graspedand/or maneuvered using a securing element or tool. The notches 230preferably extend in directions that intersect first longitudinal axis222.

[0111] Referring to FIGS. 25-27, the first section 218 of couplingelement 212 preferably includes internal threads 244 extending fromupper end 214 toward lower end 216. Coupling element 212 has a pair ofrod receiving openings 242 in communication with first bore 240 thatextend from outer surface 226 to inner surface 238 of coupling element212. The rod receiving openings 242 are adapted to seat a spinal rod(not shown) therein. The rod receiving openings 242 preferably compriseU-shaped openings having open ends adjacent upper end 214 and closedends opposite the open ends. The rod-receiving openings 242 dividecoupling element 212 into a first arm 231A and a second arm 231B.

[0112] The coupling element 212 has a cavity 246 in second section 221and a seat 250 for engaging an anchoring element. In the particularpreferred embodiment shown in FIG. 26, seat 250 is a conical-shaped seatincluding sidewalls 252 tapering inwardly toward one another adjacentlower end 216. In other preferred embodiments, seat 250 may besubstantially spherical or concave.

[0113]FIGS. 28A and 28B show a metal blank 310 used to make a couplingelement, in accordance with other preferred embodiments of the presentinvention. The metal blank 310 preferably has a cylindrical outersurface 326, a longitudinal axis designated A-A, and a lower end 316that is chamfered. The metal blank 310 is bored from upper end 314toward lower end 316 to form first bore 340 coaxial with longitudinalaxis A-A.

[0114] Referring to FIGS. 29-31, coupling element 312 has arod-receiving opening 342 that divides opposing arms 331A, 331B from oneanother. The coupling element 312 has an outer surface 326 including apair of gripping notches 30A, 30B on each opposing arm 331A, 331B. Theopposing gripping notches 330A, 330B may be secured with a tool, such asforceps (not shown).

[0115] Referring to FIGS. 30-31, the opposing pairs of gripping notches330A, 330B are cut into the respective arms 331A, 331B of couplingelement 312. In certain preferred embodiments, the gripping notches330A, 330B are formed using a rotary cutter, such as a woodruff cutter,that is abutted laterally against exterior surface 326 of couplingelement 312. A first pair of gripping notches 330A on first arm 331A areseparated from one another by a first rib 333A extending therebetween.Similarly, a second pair of gripping notches 330B on second arm 331B areseparated from one another by second rib 333B. Coupling element 312 hastwo bores extending therethrough. A first bore 340 extends in adirection substantially parallel to the axis designated A-A. The firstbore 340 is preferably formed by drilling from the upper end 314 towardthe lower end 316 of the coupling element 312. Coupling element 312 alsoincludes a second bore 341 extending from the lower end 316 toward upperend 314 along axis B-B. In certain preferred embodiments, the first andsecond bores 340, 341 may not extend completely through the length ofcoupling element 312, but may meet at an intermediate region betweenupper end 314 and lower end 316.

[0116] Referring to FIG. 31, first bore 340 is coaxial with axis A-A andsecond bore 341 is coaxial with axis B-B. The first bore 340 extendsfrom upper end 314 toward lower end 316 of coupling element 312, andsecond bore 341 extends from lower end 316 toward upper end 314. Upperend 314 of coupling element 312 defines a first plane 423 and lower end316 defines a second plane 425. The first and second planes 423, 425 arepreferably angled relative to one another and intersect one another.

[0117]FIG. 32A shows coupling element 312 including second bore 341formed from lower end 316 thereof and extending along axis B-B.Referring to FIG. 32B, first bore 340 is coaxial with axis A-A andsecond bore 341 is coaxial with axis B-B. Coupling element 312 includesinternal threads 344 extending from upper end 314 toward lower end 316.The exterior surface of coupling element 312 adjacent lower end 316 ispreferably chamfered. In certain preferred embodiments, the chamferedsurface is formed by rotating coupling element 312 about axis B-B andengaging lower end 316 with a grinding tool. An intermediate region 321of coupling element 312 includes a retaining lip 343. As will bedescribed in more detail below, retaining lip 343 prevents an anchoringelement such as a screw fastener from disassembling with couplingelement 312 after the coupling element and the anchoring element havebeen assembled together. Second bore 341 formed in lower end 316 ofcoupling element 312 preferably includes a seat 350 having side walls352 that taper inwardly toward one another. As shown in FIG. 32B-1, theside walls 352 and axis B-B preferably define an angle of approximately8-12° and more preferably about 10°.

[0118] Referring to FIGS. 33-35B, the pedicle screw assembly of thepresent invention also includes anchoring element 352 having tip end 354and head 356 remote therefrom. In certain preferred embodiments, head356 has a spherical radius. Head 356 includes evenly spaced cuts 370formed in the exterior surface of head 356. In certain preferredembodiments, the spaced cuts 370 are made using a grinding or millingtool that engages the head from lateral sides. Fastening element 352includes external screw threads 358 having an outer diameter 366 and aninner diameter 364. Fastening element 352 also includes neck 360provided between an upper end of screw threads 358 and head 356. Theneck 360 has a concave surface 362. Fastening element 352 also includesa cutting surface 371, such as a cutting flute, formed adjacent tip end354. As is known to those skilled in the art, providing a cutting flute371 at a tip end 354 of fastening element 352 avoids the need to pre-tapinto bone, which in turn provides for a tighter, snugger fit between thefastening element 352 and bone. As the fastening element 352 is screwedinto bone, the cutting flute 371 cuts into the bone, thereby avoidingthe need to pre-tap the bone. When screwing fastening element 352 inbone, the evenly spaced cuts 370 on head 356 are engaged by the fingersof a driver, as will be described in more detail below.

[0119] Referring to FIGS. 36A-36C, fixation assembly also preferablyincludes a locking element such as a set screw 390 having an upper end392, a lower end 394 and external threads 396 extending between theupper and lower ends. Set screw 390 includes a hexagonal shaped opening398 extending from upper end 392 toward lower end 394, which is adaptedto receive an end of a hexagonal driver for turning set screw 390. Aswill be described in more detail below, an underside 394 of set screw390 is adapted to abut against an orthopedic stabilizing rod forexerting a downward force on a head of an anchoring element for lockingfixation assembly from further movement.

[0120]FIG. 37A-39A show a fixation assembly including coupling element312, screw fastener 352 and set screw 390 prior to the components beingassembled together. In one preferred embodiment, the tip end 354 ofscrew fastener 352 is passed through the first bore 340 extending fromupper end 314 of coupling element 312. In certain embodiments, theexternal threads 358 of screw fastener 352 must be threaded pastinternal threads (not shown) of coupling element 312, however, in otherpreferred embodiments, the threaded portion may pass the internalthreads by rocking the threaded portion 358 back and forth until thethreaded portion 358 of screw fastener 352 clears a lower end of theinternal threads. After the threads 358 of screw fastener 352 havecleared the interval threads of coupling element 312, the head 356 ofscrew fastener 352 is press fit into seat 350 adjacent lower end 316 ofcoupling element 312. The head 356 of screw fastener 352 preferably hasa diameter that is slightly greater than the diameter of the bore atretaining lip 343. As head 356 is pushed through retaining lip 343, theretaining lip 343 is slightly deformed to allow the head to pass intoseat 350. Once head 356 passes retaining lip 343, the retaining lip 343springs back to a diameter that is smaller than the outer diameter ofhead 356. As a result, head 356 is captured in seat 350 of couplingelement 312 between retaining lip 343 and the opening at the lower end316 of coupling element 312. Once the head 356 is captured within seat350, the screw fastener 352 and coupling element 312 are able to pivotand rotate relative to one another.

[0121] Referring to FIGS. 40-42, after the head 356 of anchoring element352 has been captured within the seat 350 of coupling element 312, thebone fixation assembly is ready to be anchored into bone and coupledwith an orthopedic stabilizing rod. In one preferred embodiment, adriver 421 including shaft 423 having lower end 425 with spaced fingers427 projecting therefrom is placed in substantial alignment over head356 of screw fastener 352. The fingers 427 are preferably substantiallyrigid so as to limit flexing or bending of the fingers 427 as forces areexerted upon the fingers. The fingers 427 are then seated in spaced cuts330 of head 356. Driver 421 also includes a shaft 423 having externalthreads 429 adapted to mesh with the internal threads 344 of couplingelement 312 for stabilizing coupling element 312 and screw fastener 352as screw fastener 352 is threaded into bone. Driver 421 also preferablyincludes a sleeve 425 slidable along shaft 423 for sliding over exteriorsurface 326 of coupling element 312 to further stabilize the fixationassembly when threading fastening element 352 into bone.

[0122] Although the invention herein has been described with referenceto particular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the embodiments disclosed herein and thatother arrangements may be devised without departing from the spirit andscope of the present invention as defined by the appended claims.

1. A method of stabilizing bone comprising: providing a coupling elementhaving first and second sections that are angled relative to oneanother, said coupling element having rod receiving openings forreceiving an elongated member; assembling said coupling element with ananchoring element; after the assembling step, securing said anchoringelement in bone; moving said coupling element relative to said anchoringelement to align said rod receiving openings with said elongated member;securing said orthopedic rod in said rod receiving openings; and afterthe securing step, locking said coupling element from further movementrelative to said anchoring element.
 2. The method of claim 1, whereinsaid coupling element has a first bore extending through said firstsection and a second bore extending through said second section.
 3. Themethod of claim 2, wherein said rod receiving openings extend throughsaid first section of said coupling element in a direction transverse tosaid first bore.
 4. The method of claim 2, wherein said first and secondbores intersect one another between said upper and lower ends of saidcoupling element.
 5. The method as claimed in claim 1, wherein saidelongated member is an orthopedic rod.
 6. A method of stabilizing aspine comprising: providing a coupling element having a first borecoaxial with a first longitudinal axis and a second bore coaxial with asecond longitudinal axis, wherein said first and second longitudinalaxes are transverse to one another; assembling said coupling elementwith an anchoring element; after the assembling step, securing saidanchoring element in bone.
 7. The method as claimed in claim 5, whereinsaid coupling element has rod receiving openings for securing anorthopedic rod, the method further comprising: moving said couplingelement relative to said anchoring element to align said rod receivingopenings with said orthopedic rod; securing said orthopedic rod in saidrod receiving openings; and after the securing step, locking saidcoupling element from further movement relative to said anchoringelement.
 8. The method as claimed in claim 6, wherein said couplingelement has an upper end and a lower end, said first bore extending fromsaid upper end toward said lower end and said second bore extending fromsaid lower end toward said upper end.
 9. The method as claimed in claim8, wherein said first and second bores are in communication with oneanother between said upper and lower ends of said coupling element. 10.The method as claimed in claim 6, wherein said upper end of saidcoupling element defines a first plane and said lower end of saidcoupling element defines a second plane, and wherein said first andsecond planes intersect one another.
 11. The method as claimed in claim6, wherein said anchoring element is a separate member assembled withsaid coupling element so that said coupling element and said anchoringelement are movable relative to one another.
 12. The method as claimedin claim 6, wherein said anchoring element has a head having asubstantially spherical underside, and wherein said coupling element hasa seat at the lower end thereof.
 13. The method as claimed in claim 12,wherein said seat is shaped for facilitating pivotal movement of saidcoupling element and said anchoring element relative to one another. 14.The method as claimed in claim 13, wherein said seat is substantiallyconical with sidewalls tapering inwardly toward said lower end of saidcoupling element, and wherein the spherical underside of the head ofsaid anchoring element is adapted to engage the conical seat of saidcoupling element.
 15. The method as claimed in claim 13, wherein saidseat has a substantially concave surface adapted to engage the sphericalunderside of said head.
 16. A method of stabilizing a spine comprising:providing a coupling element having an uppermost end defining a firstplane, a lowermost end defining a second plane, and at least one boreextending from said uppermost end toward said lowermost end, whereinsaid first and second planes intersect one another; assembling saidcoupling element with an anchoring element; after the assembling step,securing said anchoring element in bone.
 17. The method as claimed inclaim 16, wherein said coupling element has rod receiving openings forsecuring an orthopedic rod, the method further comprising: moving saidcoupling element relative to said anchoring element to align said rodreceiving openings with said orthopedic rod; securing said orthopedicrod in said rod receiving openings; and after the securing step, lockingsaid coupling element from further movement relative to said anchoringelement.
 18. The method as claimed in claim 16, wherein said at leastone bore is adapted for receiving said anchoring element.
 19. The methodas claimed in claim 16, wherein said anchoring element has a head with asubstantially spherical shape and said coupling element has aconical-shaped seat adjacent said lower end thereof, and wherein saidspherical head is adapted to engage said conical seat.
 20. The method asclaimed in claim 16, wherein said rod receiving openings are defined bysubstantially U-shaped opening surfaces.